Heat exchanger



Oct. 27, 1953 M. H. HOFMEISTER HEAT EXCHANGER 2 Sheets-Sheet 1 Filed Sept. 20, 1949 lll ll.

Oct. 27, 1953 M, H. HOFMEISTER HEAT EXCHANGER.

2 Sheets-Sheet 2 Filed Sept. 20, 1949 n a W L Patented Oct. 27, 1953 HEAT EXCHANGER Maurice H. Hofmeister, Evanston, Ill., assignor to Bell & Gossett Company, Morton Grove, 111., a corporation of Illinois Application September 20, 1949, Serial No. 116,647

2 Claims.

My invention relates to heat exchangers and more particularly to a unit which is characterized by certain operating advantages in relation to the more common forms of this device.

Characteristic units are those employed in the production of hot water for domestic or factory purposes wherein the exchanger is inserted through an opening in the wall of a boiler, or it may be submerged in a separate chamber through which the heating fluid is circulated. In such units, the heating surface is provided by tubing which is bent into a helical coil, or may comprise a bank of straight tubes, the ends of the tube or tubes being connected to a header or headers, as the case may be. However the heat exchanger tubing may be arranged, the outside dimensions of the mass of tubing, measured transversely of the tubing, are limited by the size of the opening through which the exchanger is inserted for immersion.

It is therefore one object of my invention to devise a heat exchanger in which the tubes are constructed and arranged to provide the maximum heating surface in relation to the size of opening available in the boiler or other chamher.

A further object is to provide an exchanger as above indicated which is characterized by the maximum heating surface, considering the dimensions of the space occupied by the exchanger when submerged, i. e., the space included between intersecting planes which are tangent to the sides, ends, top and bottom of the mass of tubing.

A further object is to provide an exchanger as above which comprises a stack of coiled tube components which are reversely positioned with.

respect to each other from the top to the bottom of the heater.

These and further objects of the invention will be set forth in the following specification, reference being had to the accompanying drawings, and the novel means by which said objects are eiiectuated will be definitely pointed out in the claims.

In the drawings:

Fig. 1 is a schematic elevation showing the application of the heat exchanger to a hot water boiler.

Fig. 2 is an enlarged side elevation of the exchanger as it appears in Fig. 1.

Figs. 3 and 4 are views looking in the directions of the arrows 3 and 4, respectively, in Fig. 2.

Figs. 5 and 6 are, respectively, plan and side views of the uppermost coil as shown in Fig. 2.

Fig. 7 is a plan view of the coil immediately below the uppermost coil.

By way of example, the heat exchanger, designated generally by the numeral I0 in Fig. 1, will be described as a unit for the production of hot water. However, my invention has general application in the field of heat exchange, including refrigeration, and is not to be limited by the particular application disclosed.

The exchanger I9 includes a header II which is suitably attached to the outside of a hot water boiler I2 and has connected thereto inlet and outlet pipes I3 and I4, respectively. A stack or bank of tubes, indicated generally by the numeral 15, extends through an opening I6 in the boiler wall into a water space of the boiler and its lower and upper portions communicate, respectively, with the pipes I3 and I4 as presently described.

The tube stack I5 is composed of a plurality of coils I1 and I8 (see Figs. 2, 5 and '7), each of which is identically bent so far as the principal heat exchange portions thereof are concerned, the alternate coils II, including the uppermost coil, lying in the same position with respect to each other and the intervening coils I8 turned over 186 in relation to the alternate coils as hereinafter set forth. The uppermost and lowermost coils I? in the tube stack differ only from the remaining coils in that extensions I9 and 2c are provided for attachment to the header II and communication with the pipes I3 and I4, all respectively.

Each coil I1 is flat and possesses an elongated shape, all elements thereof lying in the same horizontal plane with the exception of the extensions I9 and 29 for the uppermost and lowermost coils I1, respectively. Considering the uppermost coil as shown in Figs. 5 and 6, it includes a straight leg 2| which connects at one end with the extension I9 and at the opposite end is reversely bent at 22 from which extends a straight leg 23 that is parallel to and spaced from the leg 2!. The leg 23 terminates short of the end of the extension I9 and is reversely bent at 24 towards the leg 2|. From the bend 24, a straight leg 25, positioned between the legs 2| and 23, angles towards the bend 22 and i reversely bent at 26 within the bend 22, the bends 22 and 26 being struck from the same center of curvature. A straight leg 21 extends from the bend 26 parallel to the leg 2| and included between the legs 2I and 25, and adjacent the bend 24, the leg 21 is reversely bent downwardly at 28 to lie immediately below the left end of the leg 23, as viewed in Figs. and 6 and as indicated by the numeral 29. The portion 29 is cut off at a convenient location and expanded at 30 to receive the left end of the straight leg 3| of the coil it which lies immediately below the coil Referring. to Fig. 7, it will be noted that the coil I8 is .bent in thesame manner-as the coil :1, except that, as assembled in the tube stack, the coil I8 is turned over through an angle of. 180 so that it presents the appearance as indicated in Fig. 7. Therefore, in additionto the straight leg 3|," the coil 8 successively includes a reverse bend 32, a straight leg '33"parallelto' and spaced from the leg 31, a" reverse bend 34, a straight leg which angles toward the bend a reverse bend 36 within andr'struckzfrom'.

the same center of curvature as the bend 32, a straight leg 3'! close to and parallel to the leg 3| and included between: the legs 3| and 35, and a' reverse bend 33 which extends downwardly beneath the adjacent *end of the'leg-33 to terminate in an expanded extremity 39 for receiving' the end of the leg- 2| on the underlying coil 17, this'coil obviously not including an extension 19. V V

' When the coils H and [9 are assembled inthe stack shown in Figs; 2 and 3, they are spaced from each other adjacent their respective ends by shims 40-. bled relation by clamping strips 4| which extend transversely of the upper and lower sides or the corresponding coils adjacent their ends and bridged between the strips 4| a-t'the right end of the" stack isa clamping bolt 62 which extends through the'openings 43 within the bends 2'0 and 3t; and at the left end; a pair of clamping bolts All extend through the openings 45 and 46in the coils I! and Hi Which lie inwardly of the-bends 24 and 34, all respectively, and .between the legs 2| and 2Tin the. coil l7 and between'the legs 3| and 31 in the coil l8, the legs 2|, 2|, 3| and 31 being appropriately spaced'for this purpose.

In simple terms,.the major portion of each coil may. .be regardedias composed of a number of simple shapes. For example, the coilll is formed from a'length of continuous tubing, one portion is bent into the shape of a U, including the legs 2] and 23 and the bend 22, while the other portion is bent as a flattened 8, including the legs 25 and 2] and theibendszl and. 2B, which lies between thelegs 2| and 23.

All of the components of each coiLare spaced from. each. otherso that .the full surface .of the tubing is available for heat exchange. The dis- I position described herein will provide as much as twenty-five per cent more surface .in relation to other tubingarrangements now in common use which occupy a comparable space in the fluid to which the exchangeris exposed. Afurther advantage is that the tube bank is completely drainable by gravity.

I claim:

1. A heat exchangerincluding a plurality of connected, fiatcoils placed side by side in spaced and aligned relation to each other, each coil being continuous and elongated in shape and com prising spaced, parallel first and second straight legs, a first reverse bend connecting an end of the first leg to the adjacent end of the second leg, a third straight leg disposed between the firstand second legs and connected by a second The coils are held in the'assernreverse bend to the other end of the second le the third leg angling towards the junction of the second leg with the first bend, and a fourth straight leg disposed between the first and second legs and connected at one end to the third leg by a third reverse bend positioned inwardly of the first bend, the oppositeend .of the fourth legjbeing .reversely bent and terminating beside said other end of the second leg and said opposite end of the fourth leg being connected to the first leg on the adjacent coil, all of the legs in each coillying substantially in the same plane, the

anglingro-f the thirdleg in each coil defining on opposite. sides thereof triangular openings with the-*secondandfourth legs and the alternate and intervening coils being relatively positioned so that thethird legs therein respectively angle in different directions whereby the third and fourth legs in each coil substantially register with said openings, respectively, ,in theiznmediately adjacent coils tosincrease turbulent flow. in the fiuid passingover the coils.

2. A heat exchanger including a plurality of connected fiat-coils spaced from each other and arrangedin aligned stack formation, each coil being continuousv and comprising spaced, parallel first and second legs, a first reverse bend connecting an end of the first leg to the adjacent end of the second leg, at third legdisposed between the first and second legs and connected by, a second reverse bend to the other end of the second leg, the third leg angling towards the junction of the second leg with the first bend, and afourth leg disposed between the first and second legs and connected atone endto the third leg by athird reverse bend positioned inwardly of the first bend, the opposite end of the fourth leg.- beingreversely bent and terminating beneath said other end of the second leg, and said opposite MAURICE H. HOFMEISTER.

References: Cited in the file: of' this patent UNITED STATES PATENTS Number Name Date 687,004. Crawford Nov. 19, 1901 725,737 Marrder Apr. 21, 1903 1,382,670 Price June 28, 1921 1,818,762 Setchkin Aug. 11, 1931 1,901,090 Eule et a1. Mar. 14, 1933 1,905,470 Jacobus Apr. 25, 1933 1,936,284. Bergman Nov. 21,1933 2,049,153 Bronson July 28, 1936 2,154,178 Moray Apr. 11, 1939 FOREIGN PATENTS Number Country Date 591,602 Great Britain Aug. 22, 1947 

